For the study, Sherwin and colleagues observed individual dolphins in a 260 square kilometre area in western Shark Bay, about 850 kilometres north of Perth, as they foraged, travelled and played with other dolphins.

Genetic samples were also taken and analysed for mitochondrial DNA type, which is inherited from the mother.

The team found those dolphins that lived in shallow waters, where sponges do not grow, mainly fell into a genetic group called Haplotype H.

The dolphins living in deeper water where the sponges were present were predominantly Hapoltype E or F.

Sherwin says further analysis of the deep-water dolphins show those that used the sponges as tools were all Haplotype E.

Interestingly the paper says sponging dolphins living in eastern Shark Bay are all Haplotype H.

Lead author Dr Anna Kopps says in a release that the "striking geographic distribution of a genetic sequence cannot be explained by chance".

"Our research shows that social learning should be considered as a possible factor that shapes the genetic structure of a wild animal population," she writes.

Sherwin says it has long been known that cultural actions can change selection pressure on genes.

He says among the first known examples of cultural hitchhiking is the development of lactose tolerance in humans which came as a result of earlier Europeans "drinking milk longer than they needed to".

"We'd like to think we found something like that going on with these dolphins," he says.